Medullary carcinoma of the thyroid

Medullary cancer of the thyroid is rare but of unusual biologic interest. It originates in the thyroid parafollicular or C cells that are of neural crest origin and that secrete calcitonin. Calcitonin measurements, particularly after pentagastrim administration, are useful in detecting the tumor and following its progression. Ninety percent of medullary cancers are sporadic and 10% are familial; the latter may be associated with pheochromocytoma and parathyroid hyperplasia-adenoma. Initial symptoms of both the sporadic and familial varieties include thyroid mass, diarrhea, and less often, flushing. Uninvolved members of kindreds with the disease should be followed up by repeated measurements of calcitonin after pentagastrim and calcium infusion and should be treated when a positive test result is obtained. Therapy involves total thyroidectomy plus node dissection if indicated. In addition, postoperative radiation may reduce the recurrence rate.